Chris Hipkins says the Government doesn't know how many COVID-19 patients are in hospital for the virus versus people in hospital for other issues.
There were 742 COVID-19 cases in hospital and 19 in intensive care as of Wednesday. But the COVID-19 Response Minister says it's unknown how many are actually in hospital for COVID.
"That [figure] will include some people who have gone to hospital for other things," Hipkins told AM on Thursday.
"Hospitals typically are testing just about everyone who walks in the door at the moment so some of them might even be mildly sick or asymptomatic for COVID-19 for another reason.
"That's not to say that there aren't a significant number of people in hospital with COVID, there are and that is putting our health system under pressure."
When asked whether he actually knew how many people were in hospital because of COVID, Hipkins said he doesn't "have that data'' but has asked the health system for it.
"We've asked the health system to adapt the way it records things so that we get a bit more visibility. That takes a while for them to implement those changes, but we have asked if they can do that so we can see that."
He said even though hospitalisations might not give the full picture the number of people in intensive care is a good benchmark.
"One of the measures that we look at for the degree of severity for hospitalisations is the number who require ventilation or require ICU treatment - we have 19 in ICU as of yesterday.
"That is a number that's going up but that's one we will follow very, very closely because it does help to give us an indication of the sort of severity that the health system is dealing with."
The Ministry of Health told Newshub while it's not clear exactly how many cases are actually in hospital for COVID, estimates suggest it's around three-quarters.
"We are developing a way to collect and report this data. We have one estimate that about three-quarters of reported hospitalisations are due to COVID-19 symptoms and the rest have COVID-19 'incidentally'. This is similar to the proportions reported from a US hospital study published last week," the Ministry said.
"In countries like Denmark currently it about 60 percent to 70 percent. The Ministry of Health is also unable to comment on whether hospitalised people have COVID-19 or other symptoms as we do not hold that level of detail about patients.
"There have been several outbreaks in hospital wards, which can contribute to COVID-19 hospitalisation numbers. For some of these cases, they contracted COVID-19 from an exposure in hospital. For this reason, hospitals are now routinely screening all patients being admitted."
It comes after 22,454 new community cases were reported on Wednesday.
New Zealand is in the midst of an outbreak of the highly contagious Omicron outbreak. There are cases spread across the country. On Wednesday the Government slashed the isolation period for COVID-19 cases and household contacts to a week, down from the previous 10 days.
Hipkins said on Wednesday the change, coming into effect at 11:59pm on Friday, is necessary because the current 10-day isolation requirement "is having a wider impact on many parts of our lives"
Household contacts will still need to have a rapid antigen test (RAT) at day three and day seven of their isolation period. If they become symptomatic they should also get a test, and if the result is positive, they are required to be isolated for seven days from that point.
If a person is isolating and still has symptoms after seven days, they are advised to stay home until 24 hours after symptoms resolve.
